Search results

Search Forums New Posts
  1. KrisBlueNZ

    Hello

    Hi Ross and welcome to Electronics Point :-) These days, electronics hobbyists are a category of "makers" and they hang out at "Makerspaces" - Google makerspace in your area :-)
  2. KrisBlueNZ

    Power supply ( voltage regulator )

    Just in case someone accidentally connects the DC the wrong way round.
  3. KrisBlueNZ

    Stage Line 500W amp repair project

    Yes, you're absolutely right. The BC54x transistors use the European pinout, which is the mirror image of the American pinout that the MPSAxx transistors have. There's also a Japanese pinout, and a fourth pinout that's used for some transistors that operate at high frequecies (radio, etc)...
  4. KrisBlueNZ

    Switching power supply voltage drops under load

    Standard electrolytics aren't suitable and will fail. You need low-ESR components. As I said, I would replace all electrolytics in the output section that are the same brand as the ones that failed. OK, Digi-Key will definitely have suitable replacements. Can you make a list of the "Samxon"...
  5. KrisBlueNZ

    Sony Receiver STR - DA555ES Displays "protection fan" when turned on.

    OK, what did you "test" when you cut the wire? Did you put in a new fuse and see whether it blew or not? Did it blow? If the short is on the digital board, which I think it is, then the fuse would not blow when that wire is cut. We need to check that the 3.3V rail from the regulator is the...
  6. KrisBlueNZ

    Power supply ( voltage regulator )

    You would still need a smoothing capacitor. There's only room on that board for a small capacitor, like the 0.1 µF and 0.33 µF ones you mentioned. That board is designed to be powered from DC. You can easily get off-line (mains-powered) power supplies with DC output. The one I suggested had a...
  7. KrisBlueNZ

    Power supply ( voltage regulator )

    I don't know what that is, but it has an AC output! You can't connect that directly to a regulator; you would need a rectifier and smoothing capacitor. If you're going to buy a power supply, why not just buy an off-line DC power supply with 5V output...
  8. KrisBlueNZ

    Need assistance with 555 Timer Circuit

    The 555 is not very accurate and not designed for periods as long as five minutes. A better idea is to use a CD4060. Here's a circuit with Digi-Key part numbers for all of the components. LED1 (green) flashes to indicate that the circuit is running. LED2 (yellow) lights when the output is...
  9. KrisBlueNZ

    Stage Line 500W amp repair project

    Also, Q7 and the corresponding transistor in the right channel will need to be held in contact with the heatsink. Can you think of any way to do this? You can use a small amount of thermal paste to get heat conduction but you really need some way to hold them together with some pressure.
  10. KrisBlueNZ

    Stage Line 500W amp repair project

    Yes that's the right pinout for the BC547/8/9 and BC557/8/9. So the voltages you marked on the schematic in post #144 have the collector and emitter reversed. That's no problem. Those voltages are reasonable. Is the left channel fault LED still lit?
  11. KrisBlueNZ

    LM386 Amplifier Module help

    I guess your choice of speakers and enclosure will be pretty important. Perhaps you could find a forum for discussion of acoustics, and describe your whole project in detail - don't force them to play guessing games with you, please - and see what they suggest. We can advise on the electronics...
  12. KrisBlueNZ

    Power supply ( voltage regulator )

    I think he has a circuit board that already has a position for a three-terminal regulator. So he should use a 7805 (in which case he may need a heatsink depending on the actual voltage he provides) or a drop-in switching regulator such as one of these...
  13. KrisBlueNZ

    Sony Receiver STR - DA555ES Displays "protection fan" when turned on.

    OK, that's the 3.3V rail. That wire goes to the "main board" but it isn't used there. It's used on the "Digital Board". It arrives at the board at the bottom of page 20 of the service manual, on pin "4-4". From there, it powers the Audio DSP, IC1112, and a lot of other ICs on that board. Do you...
  14. KrisBlueNZ

    Switching power supply voltage drops under load

    Hi there. Yes, that could very well be the problem. Bulging indicates overheating and venting has occurred, and this reduces the capacitance and increases the ESR of the capacitor, which increases the heating, and so on. So their days have been numbered for a while now. When some electrolytics...
  15. KrisBlueNZ

    Amplifier?

    There are hundreds of DIY amplifier projects out there on the net! If you're going to the trouble of building something, why not make something half way decent? And the LM386 does not fall in that category! An excellent site to look at is Rod Elliott's ESP site at http://sound.westhost.com. He...
  16. KrisBlueNZ

    Help on 74LS165

    Why 74165? That's an obsolete TTL device! Do you mean 74HC165? If not, why not? OK, I don't know what you mean but as long as you do, that's fine :) When you're cascading so many HC165s like that, the chance of a bogus clock occurring because of noise increases, and so does the potential...
  17. KrisBlueNZ

    230v relay switching problem with rf

    So do you want the relay to turn ON when RF is present, and turn OFF when it isn't? As Adam asked, what is the frequency and amplitude of the RF? How are you getting the RF into that circuit? You say the relay doesn't turn off "at the right time". Can you explain? Does it turn off too late...
  18. KrisBlueNZ

    230v relay switching problem with rf

    Why?! A relay can switch around 100 times per second. An RF signal alternates at least 100,000 times per second. What are you trying to do?
  19. KrisBlueNZ

    230v relay switching problem with rf

    Hi there and welcome to Electronics Point :-) I don't think I understand your question. Are you using the relay contacts to switch an RF (radio frequency) signal? It looks like you are using them to switch mains power ON and OFF. And you mentioned an industrial bell as a load. I don't see how...
  20. KrisBlueNZ

    Help on 74LS165

    Hi Daniel, For a 74xx or 74LSxx device, unconnected inputs will float at around 3V and will be considered high by the device (though you're not supposed to rely on that). You need to link them to 0V if you want them to be considered low by the device. All inputs on digital devices are supposed...
Top